TWI383999B - Acrylic thermal plastic resin and formed article for optical material - Google Patents

Description

Acrylic thermoplastic resin and molded body for optical material

The present invention relates to an acrylic thermoplastic resin having excellent optical properties, and a molded article for an optical material comprising the acrylic thermoplastic resin.

In recent years, with the advancement of flat-panel displays such as liquid crystal display devices, plasma displays, and organic EL display devices, infrared sensors, optical waveguides, etc., it is required to have excellent transparency not only for optical materials used in such optical materials, but also for High heat resistance and high optical equivalence (also known as low birefringence).

For example, as the size of the flat panel display increases, the molded body for the optical material required for the enlargement also increases in size, and the birefringence distribution occurs due to the deflection of the external force, so that the contrast is lowered. In order to reduce the birefringence distribution, a change in birefringence due to an external force is sought, that is, a material having a small absolute value of the photoelastic coefficient.

In addition, with the enlargement of the flat panel display, the result is not only viewed from the front but also from the oblique direction. At this time, in the principle of the display device, there is a problem that the display color changes or the contrast is lowered due to the viewing direction. In order to improve the viewing angle characteristics, a material having a small absolute value of birefringence is sought.

A methacrylic resin represented by a single polymer of methyl methacrylate (PMMA) is excellent in transparency and small in birefringence, so it can be used as a material having optical isotropic properties for various opticals. use. However, the material properties required in the market are now changing to require less miniaturization, smaller birefringence changes due to external forces, and higher heat resistance, and it is expected to develop materials that simultaneously satisfy these characteristics ( Non-patent documents 1, 2).

In the case of the prior art of the present invention, for example, among the four kinds of monomers constituting the acrylic thermoplastic resin of the present invention, benzyl methacrylate is removed, and methyl methacrylate, styrene, and maleic acid are used. The ternary copolymer formed by Xuan has been disclosed in Patent Documents 1 to 3 and the like. Patent Document 1 discloses that the weight ratio (a/b) of the content (a) of the repeating unit derived from the vinyl aromatic monomer to the content (b) of the cyclic acid anhydride repeating unit in the ternary copolymer is 1 If it is less than 3, it is preferable in terms of heat deformation resistance and weather resistance. On the other hand, Patent Document 2 does not describe the content ratio (a/b) and the effect that can be expected from the range, and only the third embodiment in which a/b = 14/10 and more than 1 is described in the embodiment. Copolymer. Similarly, Patent Document 3 does not describe the weight ratio (a/b) of the content (a) of the repeating unit derived from the vinyl aromatic monomer and the content (b) of the cyclic acid anhydride repeating unit, and The effect that can be expected in the range is only a ternary copolymer having a/b = 15/12 and more than 1 in the examples.

Further, Patent Document 4 describes a copolymer composed of any one or more of methyl methacrylate and a monomer copolymerizable with a monomer selected from the group consisting of styrene, benzyl methacrylate, and maleic anhydride. It is described that one of the constituents constituting the thermoplastic antistatic laminate is not mentioned at all. Further, there is no embodiment corresponding to the quaternary copolymer of the present invention.

Further, Patent Document 5 describes a copolymer containing styrene, maleic anhydride, and methacrylate. Specifically, it is described in the copolymer that methyl methacrylate or benzyl methacrylate as a methacrylate can be copolymerized. However, there is no description in the literature regarding the quaternary copolymer of methyl methacrylate and styrene, benzyl methacrylate or maleic anhydride of the present invention. Further, it is also described in the literature that in the case of methacrylic esters, esters composed of lower alkyl groups are preferred, and methacrylates derived from aromatic groups derived from the present invention are not taught at all. Repeat unit. Further, a copolymer which is a part or all of the maleic anhydride which is a constituent unit and which is a hydrolyzate is preferably a resin.

Further, Patent Document 6 describes a copolymer containing a monomer selected from the group consisting of styrenes, maleic anhydrides, and methacrylates as a main component. In this document, although the monomer of the methacrylate is exemplified by methyl methacrylate or benzyl methacrylate, specifically, a copolymer composed of styrene and methacrylate is described. And a mixture of a copolymer of maleic acid and methacrylic acid ester, a copolymer composed of styrene and maleic acid, and a mixture of maleic anhydride and methacrylic acid ester. The mixture of the copolymers does not mention the effect obtained when simultaneously copolymerizing three or more kinds of monomers. In particular, no examples of the 4-membered copolymer of the present invention are described. It is also described in the literature that the methacrylate in the copolymer is preferably an ester composed of a lower alkyl group, and the methacrylate derived from the aromatic group is not taught at all. Repeat unit. Further, a copolymer which is a part or all of the maleic acid constituting unit and which is a hydrolyzate is preferably a resin.

Further, Patent Document 7 describes a copolymer of maleic anhydride and acrylate. Specifically, it is described that methyl (meth) acrylate or benzyl (meth) acrylate may be used in combination as an acrylate monomer in the copolymer, and it may be described as being in another range without impairing heat resistance. The styrenes of the body are copolymerized. However, no examples of the 4-membered copolymer of the present invention are described.

[Patent Document 1] Japanese Patent No. 1704667

[Patent Document 2] Japanese Patent No. 28889893

[Patent Document 3] Japanese Patent Laid-Open No. Hei 5-288929

[Patent Document 4] Japanese Patent Laid-Open No. Hei 8-85729

[Patent Document 5] Japanese Patent No. 3521374

[Patent Document 6] Japanese Patent No. 3711666

[Patent Document 7] Japanese Patent Laid-Open Publication No. 2007-261265

[Non-Patent Document 1] General Chemistry, .39, 1988 (publishing of the Society Publishing Center)

[Non-Patent Document 2] Display Monthly, April issue, 2005

An object of the present invention is to provide an acrylic thermoplastic resin excellent in optical properties and a molded article for an optical material comprising the acrylic thermoplastic resin.

The present invention is based on the discovery of a molded article for an optical material composed of a specific acrylic thermoplastic resin. For example, if it is an optical film, it can simultaneously achieve low birefringence and low photoelastic coefficient when compared with a conventional optical film. The present invention has been completed by discovering this surprising fact.

That is, the present invention relates to the following:

[1] An acrylic thermoplastic resin containing a repeating unit derived from a methacrylate monomer represented by the following formula (1) and a vinyl aromatic monomer derived from the following formula (2) a repeating unit, a repeating unit derived from a methacrylic ester monomer having an aromatic group represented by the following formula (3), and a cyclic acid represented by the following formula (4) or the following formula (5) Xuan repeat unit;

(wherein R ¹ represents hydrogen, a linear or branched chain having 1 to 12 carbon atoms, and a carbon number of 5 to 12 cycloalkyl groups)

(wherein R ² and R ³ each may be the same or different and represent a hydrogen, a halogen, a hydroxyl group, an alkoxy group, a nitro group, a linear or branched chain having an alkyl group having 1 to 12 carbon atoms; and 1 represents 1; To the integer of 3)

(wherein R ⁴ represents hydrogen, halogen, hydroxy, alkoxy, nitro, a linear or branched chain having 1 to 12 carbon atoms; m represents an integer of 1 to 3, and n represents 0 to 2 Integer)

(wherein R ⁵ to R ⁸ may be the same or different, respectively, and represent an alkyl group having 1 to 12 carbon atoms in a hydrogen, a linear or a branched chain).

[2] The acrylic thermoplastic resin according to [1], wherein the weight average molecular weight measured by the GPC measurement is in the range of 10,000 to 400,000, and the molecular weight distribution is in the range of 1.3 to 3.0.

[3] The acrylic thermoplastic resin according to [1] or [2], which comprises 10 to 70% by weight of the repeating unit derived from the methacrylate monomer represented by the formula (1), and the formula (2) 5 to 40% by weight of the repeating unit derived from the vinyl aromatic monomer, and 0.1 to 5% by weight of the repeating unit derived from the methacrylic ester monomer having an aromatic group represented by the formula (3), 4) or the cyclic acid anhydride repeating unit represented by the formula (5) is 20 to 50% by weight.

[4] The acrylic thermoplastic resin according to any one of [1] to [3] wherein the content of the repeating unit derived from the vinyl aromatic monomer (A) and the content of the cyclic acid repeating unit The molar ratio (B/A) of (B) is greater than 1 and below 10.

[5] The acrylic thermoplastic resin according to any one of [1] to [4] wherein the repeating unit derived from the methacrylate monomer is derived from methyl methacrylate, which is derived from a vinyl group. The repeating unit of the aromatic monomer is derived from styrene, and the repeating unit derived from the methacrylic ester monomer having an aromatic group is derived from benzyl methacrylate, and the cyclic acid repeat unit is derived from Malay Acid Xuan.

[6] The acrylic thermoplastic resin according to any one of [1] to [5], which is an optical property satisfying the following (i):

(i) The absolute value of the photoelastic coefficient is 3.0 × 10 ^-12 Pa ^-1 or less.

[7] The acrylic thermoplastic resin according to any one of [1] to [6] which is an optical property satisfying the following (ii):

(ii) In the least square approximation linear relationship (a) of the extended birefringence (⊿n(S)) and the stretching ratio (S), the value of the slope K satisfies the following formula (b):

⊿n(S)=K×S+C ...(a)

∣K∣<0.30×10 ^-6 ...(b)

[8] The acrylic thermoplastic resin according to any one of [1] to [7], which further satisfies the optical properties of (iii) below:

(iii) The absolute value of the phase difference (Re) in the in-plane direction is 30 nm or less.

[9] The acrylic thermoplastic resin according to any one of [1] to [8] which further satisfies the optical properties of the following (iv):

(iv) The absolute value of the phase difference (Rth) in the thickness direction is 30 nm or less.

[10] The acrylic thermoplastic resin according to any one of [1] to [9], which further satisfies the optical properties of (v) below:

(v) The ratio (Rth/Re) of the phase difference (Re) in the in-plane direction to the phase difference (Rth) in the thickness direction satisfies the following formula (c):

0.1<Rth/Re<1 ...(c)

[11] The acrylic thermoplastic resin according to any one of [1] to [10], which further satisfies the following condition (vi):

(vi) The glass transition temperature (Tg) is 120 ° C or higher.

[12] The acrylic thermoplastic resin according to any one of [1] to [11], which further satisfies the following condition (vii):

(vii) The total light transmittance is 85% or more.

[13] A molded article for an optical material, which is composed of the acrylic thermoplastic resin according to any one of [1] to [12].

[14] The molded article for an optical material according to [13], which is an optical film.

[15] The molded article for an optical material according to [14], wherein the optical film is a film formed by extrusion molding, and is formed to extend at least in a uniaxial direction, and has a stretching ratio of 0.1 to 300%. .

[16] The molded article for an optical material according to [14], wherein the optical film is a film formed by casting, and is stretched at least in a uniaxial direction, and has a stretching ratio of 0.1 to 300%.

[17] The molded article for an optical material according to [14], wherein the optical film is a polarizing plate protective film.

[18] The molded article for an optical material according to [14], wherein the optical film is a retardation film.

[19] The molded article for an optical material according to [13], which is an optical lens.

According to the invention, it is possible to provide an acrylic thermoplastic resin excellent in optical properties and a molded article for an optical material comprising the acrylic thermoplastic resin. In particular, it is possible to provide an acrylic thermoplastic resin excellent in at least one of optical properties, birefringence, and retardation, and a molded article for an optical material comprising the acrylic thermoplastic resin.

[Acrylic thermoplastic resin]

The acrylic thermoplastic resin of the present invention is composed of a repeating unit derived from a methacrylate monomer represented by the following formula (1) and a vinyl aromatic group represented by the following formula (2). a repeating unit of a group monomer, a repeating unit derived from a methacrylic acid ester monomer having an aromatic group represented by the following formula (3), and a formula (4) or a formula (5) below Cyclic acid Xuan repeat unit;

(wherein R ¹ represents hydrogen, a linear or branched chain having 1 to 12 carbon atoms, and a carbon number of 5 to 12 cycloalkyl groups)

(wherein R ² and R ³ each may be the same or different and represent a hydrogen, a halogen, a hydroxyl group, an alkoxy group, a nitro group, a linear or branched chain having an alkyl group having 1 to 12 carbon atoms; and 1 represents 1; To the integer of 3)

(wherein R ⁴ represents hydrogen, halogen, hydroxy, alkoxy, nitro, a linear or branched chain having 1 to 12 carbon atoms; m represents an integer of 1 to 3, and n represents 0 to 2 Integer)

(wherein R ⁵ to R ⁸ may be the same or different, respectively, and represent an alkyl group having 1 to 12 carbon atoms in a hydrogen, a linear or a branched chain).

In the acrylic thermoplastic resin, the repeating unit represented by the formula (1) is derived from a methacrylic acid and a methacrylic acid ester monomer, and the methacrylate used may, for example, be methyl methacrylate or methacrylic acid. Ethyl ester, propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, 2-ethylhexyl methacrylate, methyl Cyclohexyl acrylate and the like. Methacrylic acid and methacrylic acid ester may be used alone or in combination of two or more.

Among these methacrylates, alkyl methacrylate having an alkyl group having a carbon number of 1 to 7 is preferred, and since the obtained acrylic thermoplastic resin is excellent in heat resistance and transparency, it is characterized by methyl methacrylate. good.

From the viewpoint of transparency, the content of the repeating unit represented by the formula (1) is preferably from 10 to 70% by mass, preferably from 25 to 70% by mass, more preferably from 40 to 70% by mass. .

The repeating unit represented by the formula (2) is derived from an aromatic vinyl monomer. The monomers to be used may, for example, be styrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 2,4-dimethylstyrene, 2,5-dimethylbenzene. Ethylene, 2-methyl-4-chlorostyrene, 2,4,6-trimethylstyrene, α-methylstyrene, cis-β-methylstyrene, trans-β-methylbenzene Ethylene, 4-methyl-α-methylstyrene, 4-fluoro-α-methylstyrene, 4-chloro-α-methylstyrene, 4-bromo-α-methylstyrene, 4- Tributylstyrene, 2-fluorostyrene, 3-fluorostyrene, 4-fluorostyrene, 2,4-difluorostyrene, 2-chlorostyrene, 3-chlorostyrene, 4-chlorostyrene , 2,4-dichlorostyrene, 2,6-dichlorostyrene, 2-bromostyrene, 3-bromostyrene, 4-bromostyrene, 2,4-dibromostyrene, α-bromobenzene Ethylene, β-bromostyrene, 2-hydroxystyrene, 4-hydroxystyrene, and the like. These aromatic vinyl monomers may be used alone or in combination of two or more.

Among these monomers, styrene or α-methylstyrene is preferred because of easy copolymerization.

The content of the repeating unit represented by the formula (2) is preferably from 5 to 40% by mass, preferably from 5 to 30% by mass, and from 5 to 20% by mass, more preferably from the viewpoints of transparency and heat resistance. good.

Since the acrylic thermoplastic resin of the present invention contains a repeating unit represented by the formula (3), it can exhibit heat resistance and birefringence, and can exhibit optical characteristics in which the photoelastic coefficient is further minimized.

The repeating unit represented by the formula (3) is derived from a methacrylate monomer having an aromatic group. The monomer to be used may, for example, be phenyl methacrylate, benzoic acid methacrylate or 1-phenylethyl methacrylate. These monomers may be used alone or in combination of two or more. Among these monomers, benzyl methacrylate is particularly preferred.

The content of the repeating unit represented by the formula (3) is preferably from 0.1 to 5% by mass, from the viewpoint of further exhibiting the optical characteristics of the effect of the present invention (especially, the low photoelastic coefficient described later is extremely small). It is preferably from 0.1 to 4% by mass, more preferably from 0.1 to 3% by mass.

The cyclic acid repeating unit represented by the formula (4) is derived from an unsubstituted and/or substituted maleic anhydride. The monomers to be used may, for example, be maleic anhydride, citraconic anhydride, dimethyl maleic anhydride, dichloromaleic anhydride, brominated maleic anhydride, dibrominated maleic anhydride, phenyl mala Anhydride, diphenylmaleic anhydride, and the like. Among these monomers, maleic anhydride is particularly preferred because of easy copolymerization.

Further, the cyclic acid anhydride repeating unit represented by the formula (4) is derived from a condensation cyclization reaction between repeating units to be described later, and examples thereof include glutaric anhydride and the like.

In the acrylic thermoplastic resin of the present invention, the cyclic acid anhydride repeating unit represented by the formula (4) or the formula (5) may be partially hydrolyzed and opened by an external environment such as moisture in the air. In the acrylic resin of the present invention, the hydrolysis rate is preferably less than 10 mol% from the viewpoint of optical properties and heat resistance. It is more preferably less than 5 mol%, and is preferably less than 1 mol%.

Here, the hydrolysis rate (% by mole) is determined by {1 - (amount of cyclic anhydride after hydrolysis (mole)) / amount of cyclic anhydride before hydrolysis (mole)} × 100.

In order to achieve a high degree of heat resistance and optical characteristics (especially, control of a phase difference described later) which is an effect of the present invention, the content ratio of the cyclic acid anhydride repeating unit represented by the formula (4) or the formula (5) is 20 It is preferably 50% by mass or more, preferably 20 to 45% by mass. However, in the acrylic thermoplastic resin of the present invention, the content (A) of the repeating unit derived from the vinyl aromatic monomer represented by the formula (2) and the ring represented by the formula (4) or (5) The molar ratio (B/A) of the content (B) of the acid repeating unit is preferably more than 1 and preferably 10 or less, more preferably more than 1 and more preferably 5 or less.

The weight average molecular weight (Mw) in terms of PMMA measured by the GPC measurement method of the acrylic thermoplastic resin of the present invention is in the range of 10,000 to 400,000, preferably in the range of 40,000 to 300,000, and in the range of 70,000 to 200,000. More preferably, the molecular weight distribution (Mw/Mn) is in the range of 1.8 to 3.0, preferably in the range of 1.8 to 2.7, and more preferably in the range of 1.8 to 2.5.

The glass transition temperature (Tg) of the acrylic thermoplastic resin of the present invention can be arbitrarily controlled by the resin composition, but it is preferably adjusted to 120 ° C or higher from the viewpoint of industrial applicability. Further, it is more preferably controlled to be 130 ° C or more, and it is particularly preferable to adjust to 135 ° C or more.

[Polymerization]

The polymerization method of the acrylic thermoplastic resin of the present invention can be generally carried out by a polymerization method such as cast polymerization, bulk polymerization, suspension polymerization, solution polymerization, emulsion polymerization or anionic polymerization, but it is used for optical materials. In other words, it is preferable to avoid the incorporation of small foreign matter as much as possible. From this point of view, it is preferable to carry out casting polymerization and solution polymerization without using a suspending agent or an emulsifier.

Further, as the polymerization form, for example, either a batch polymerization method or a continuous polymerization method can be used, but from the viewpoint of obtaining a polymer having a more uniform composition, it is preferred to use a continuous polymerization method.

The temperature and the polymerization time in the polymerization reaction vary depending on the kind and ratio of the monomers to be used, for example, the polymerization temperature is preferably from 0 to 150 ° C, the polymerization time is preferably from 0.5 to 24 hours, and the polymerization temperature is more preferably 80. The polymerization time is preferably from 1 to 12 hours up to 150 °C.

When a solvent is used for the polymerization reaction, the polymerization solvent may, for example, be an aromatic hydrocarbon solvent such as toluene, xylene or ethylbenzene; a ketone solvent such as methyl ethyl ketone or methyl isobutyl ketone; or an ether such as tetrahydrofuran. Solvents, etc. These solvents may be used alone or in combination of two or more. When the boiling point of the solvent to be used is too high, the residual volatile component of the obtained acrylic thermoplastic resin is increased. Therefore, a solvent having a boiling point of 50 to 200 ° C is preferred.

At the time of the polymerization reaction, a polymerization initiator may be added as needed.

As the polymerization initiator, any of the initiators used in general radical polymerization can be used, and examples thereof include cumene hydroperoxide, diisopropylbenzene hydroperoxide, and di(tert-butyl peroxide). , oxidized lauryl sulfhydryl, benzammonium peroxide, t-butyl peroxyisopropyl carbonate, t-amylperoxy-2 -ethylhexanoate) and other organic peroxides; 2,2'-azobis(isobutyronitrile), 1,1'-azobis(cyclohexanecarbonitrile), 2,2'-azobis (2, An azo compound such as 4-dimethylvaleronitrile or dimethyl 2,2'-azobisisobutyrate. These polymerization initiators may be used alone or in combination of two or more.

The amount of the polymerization initiator to be used can be appropriately determined depending on the combination of the monomers, the reaction conditions, and the like, and is not particularly limited, but is preferably in the range of 0.005 to 5% by weight.

Any molecular weight modifier used in the polymerization reaction may be used as it is, and particularly preferred examples thereof include butyl mercaptan, octyl mercaptan, dodecyl mercaptan, and sulfur. A thiol compound such as 2-ethylhexyl glycolate. The concentration range of the molecular weight modifiers added is such that the degree of polymerization is adjusted to the above range.

In the polymerization reaction, in order to suppress gelation of the polymerization reaction liquid, the concentration of the acrylic thermoplastic resin formed in the polymerization reaction liquid is preferably adjusted to 50% by mass or less. Specifically, when the concentration of the acrylic thermoplastic resin formed in the polymerization reaction liquid is more than 50% by mass, it is preferred to adjust the polymerization solvent to 50% by mass or less by appropriately adding the polymerization solvent to the polymerization reaction liquid. The concentration of the acrylic thermoplastic resin formed in the polymerization reaction liquid is preferably 45% by mass or less, and more preferably 40% by mass or less.

The concentration of the acrylic thermoplastic resin formed in the polymerization reaction liquid is preferably 10% by mass or more, and more preferably 20% by mass or more, from the viewpoint of ensuring productivity.

The form in which the polymerization solvent is appropriately added to the polymerization reaction liquid is not particularly limited. For example, a polymerization solvent may be continuously added, or a polymerization solvent may be added intermittently. By controlling the concentration of the acrylic thermoplastic resin formed in the polymerization reaction liquid, the gelation of the reaction liquid can be more sufficiently suppressed. The polymerization solvent to be added may be, for example, the same type of solvent as the solvent used in the initial preparation of the polymerization reaction, or may be a different type of solvent, but it is preferred to use the same solvent as the solvent used in the initial preparation of the polymerization reaction. . Further, the polymerization solvent to be added may be a single solvent of only one type, or a mixed solvent of two or more types.

[condensation cyclization reaction]

In the acrylic thermoplastic resin of the present invention, the acrylic thermoplastic resin containing the cyclic acid repeating unit represented by the formula (5) is contained in the formula (1), the formula (2), and the formula (3). The acrylic thermoplastic resin of the repeating unit shown is subjected to heat treatment to be a derivative.

That is, by performing heat treatment, between the repeating units represented by the formulas (1) and (3), a condensation cyclization reaction as shown in the following (i), (ii) is caused:

It is derived by producing a cyclic acid repeating unit represented by the formula (5).

The acrylic thermoplastic resin of the present invention has high heat resistance and high optical isotropic properties by forming the cyclic acid anhydride repeating unit. When the reaction rate of the condensation cyclization reaction is insufficient, the optical isotropic property is lowered and the degree of improvement in heat resistance is insufficient. Further, in some cases, a condensation reaction may occur during the molding process due to heat treatment during molding, resulting in gelation, generation of water or alcohol, and occurrence of bubbles or silver streaks in the molded article.

In order to accelerate the condensation cyclization reaction, a method known as a conventionally known method, for example, a method in which a polymerization reaction liquid containing a solvent obtained by a polymerization step is directly subjected to heat treatment; in the presence of a solvent, if necessary, a method of performing heat treatment in the presence of a closed loop catalyst; a method of performing heat treatment using a heating furnace having a vacuum device or a devolatilizer for removing volatile components, or an extruder having a reaction device or a devolatilizer; Wait.

In the condensation cyclization reaction, the following closed-loop catalyst can be used as needed: for example, an esterification catalyst such as p-toluenesulfonic acid or a transesterification catalyst; organic acids such as acetic acid, propionic acid, benzoic acid, acrylic acid, methacrylic acid, etc. A carboxylic acid; a basic compound, an organic carboxylate, a carbonate or the like disclosed in JP-A-61-254608 or JP-A-61-261303; and an organic phosphorus compound.

The organophosphorus compound may, for example, be an alkyl (aryl) phosphinic acid such as methyl phosphonous acid, ethylphosphinic acid or phenylphosphinic acid (however, these may also belong to mutual mutation). Alkyl (aryl) phosphinic acid of the structure and such monoesters or diesters; dimethyl phosphinic acid, diethylphosphinic acid, diphenylphosphinic acid, benzene Dialkyl (aryl) phosphinic acid such as methyl phosphinic acid or phenylethylphosphinic acid and such esters; methyl phosphonic acid, ethylphosphonic acid, trifluoromethyl An alkyl (aryl) phosphonic acid such as phosphonic acid or phenylphosphonic acid and such monoesters or diesters; methyl phosphinous acid, ethyl phosphinic acid, phenylphosphinium Alkyl (aryl) phosphinic acid such as acid and such esters; methyl phosphite, ethyl phosphite, phenyl phosphite, dimethyl phosphite, diethyl phosphite, diphenyl phosphite , phosphite monoester, diester or triester such as trimethyl phosphite, triethyl phosphite, triphenyl phosphite; methyl phosphate, ethyl phosphate, 2-ethylhexyl phosphate, isodecyl phosphate , lauryl phosphate, Acid stearyl ester, isostearyl phosphate, phenyl phosphate, dimethyl phosphate, diethyl phosphate, di(2-ethylhexyl) phosphate, octyl phosphate, diisononyl phosphate, dilauryl phosphate , distearyl phosphate, diisostearyl phosphate, diphenyl phosphate, trimethyl phosphate, triethyl phosphate, triisodecyl phosphate, trilauryl phosphate, tristearyl phosphate, triisophosphoric acid Phosphate monoester, diester or triester such as lipoester or triphenyl phosphate; methyl phosphine, ethyl phosphine, phenylphosphine, dimethyl phosphine, diethyl phosphine, diphenyl phosphine, trimethyl phosphine, Mono-, di- or tri-alkyl (aryl) phosphines such as triethylphosphine and triphenylphosphine; methylphosphine dichloride, ethyl phosphine dichloride, phenylphosphine dichloride, dimethylphosphine chloride, Alkyl (aryl) phosphine halides such as diethylphosphine chloride and diphenylphosphine; phosphine oxide, ethionyl oxide, phenylphosphine oxide, dimethylphosphine oxide, diethylphosphine oxide, diphenylphosphine oxide, oxidized trimethyl Oxidized mono-, di- or tri-alkyl (aryl) phosphine such as phosphine, triethylphosphine oxide or triphenylphosphine oxide; tetradecane chloride, tetraethyl sulfonium chloride, tetraphenylphosphonium chloride or the like (Fang), etc.

These compounds may be used singly, but in some cases, two or more kinds may be used together to enhance the effect.

The amount of the catalyst used for carrying out the condensation cyclization reaction is, for example, preferably 0.001 to 5% by mass, preferably 0.01 to 2.5% by mass, and 0.01 to 1% by mass based on the acrylic thermoplastic resin. More preferably, it is particularly preferably 0.05 to 0.5% by mass. When the amount of the catalyst used is less than 0.001% by mass, the reaction rate of the condensation cyclization reaction may not be sufficiently improved. On the other hand, when the amount of the catalyst used exceeds 5% by mass, the obtained acrylic thermoplastic resin may be colored or the acrylic thermoplastic resin may be crosslinked to be difficult to melt-form.

The period of addition of the catalyst is not particularly limited. For example, it may be added at the beginning of the reaction, may be added during the reaction, or may be added during the two periods.

Further, the condensation cyclization reaction is preferably carried out in the presence of a solvent, and a devolatilization step is preferably carried out while performing the condensation cyclization reaction. At this time, since the water or the alcohol generated by the condensation cyclization reaction is forcibly devolatilized, the equilibrium state of the reaction becomes favorable for the formation of the condensed cyclized product.

[De-swinging step]

The devolatilization step refers to removing the volatile component (i) such as a polymerization solvent or a residual monomer, and/or water or alcohol (ii) produced by a condensation cyclization reaction under reduced pressure heating as needed. step. When the removal treatment is insufficient, the amount of the remaining volatile components in the obtained thermoplastic resin increases, and the coloring due to deterioration during molding or the like causes coloring or formation failure such as bubble or silver streaks.

Examples of the apparatus used in the devolatilization step include a devolatilizer comprising a heat exchanger and a devolatilizer, an extruder having a discharge port, and a devolatilizer and an extruder arranged in series. When an extruder having a discharge port is used, the discharge holes may be one or plural, and it is preferable to have a plurality of discharge holes.

The reaction treatment temperature is preferably from 150 to 350 ° C, more preferably from 200 to 300 ° C. When the reaction treatment temperature is less than 150 ° C, the cyclization condensation reaction may become insufficient to increase the amount of residual volatile components. On the other hand, when the reaction treatment temperature exceeds 350 ° C, the coloring and decomposition of the obtained thermoplastic resin may be caused.

The reaction treatment pressure is preferably 931 to 1.33 hpa (700 to 1 mmHg), and more preferably 798 to 66.5 hpa (600 to 50 mmHg). When the reaction pressure exceeds 931 hpa (700 mmHg), volatile components containing water or alcohol tend to remain. On the contrary, if the reaction pressure is less than 1.33 hpa (1 mmHg), it is industrially difficult to carry out.

The reaction treatment time can be appropriately selected depending on the condensation cyclization rate and the amount of the remaining volatile component. However, in order to suppress the coloring and decomposition of the obtained acrylic thermoplastic resin, the reaction treatment time is preferably as short as possible.

When the acrylic thermoplastic resin of the present invention is used for optical applications, the number of foreign matters contained therein is preferably as small as possible. In the method of reducing the number of foreign matters, for example, in the polymerization reaction step, the condensation cyclization reaction step, the devolatilization step, and the molding step, the solution or the melt of the acrylic thermoplastic resin is, for example, filtered to a precision of 1.5. A method of filtering to a 15 μm Leaf-disc type polymer filter or the like.

[Formed body for optical materials]

In the molded article for an optical material comprising the acrylic thermoplastic resin of the present invention, for example, an optical film, an optical lens or the like, various additives may be contained within a range that does not significantly impair the effects of the present invention. The type of the additive is not particularly limited as long as it is generally used for blending a resin or a rubbery polymer.

For example, pigments such as inorganic fillers and iron oxides; stearic acid, behenic acid, zinc stearate, calcium stearate, magnesium stearate, and ethyl bis-stearylamine Lubricating agent; mold release agent; paraffin-based processing oil, naphthenic processing oil, aromatic processing oil, paraffin, organic polyoxane, mineral oil and other softeners/plasticizers; hindered phenolic resistance Antioxidants such as oxidizing agents and phosphorus-based heat stabilizers; hindered amine-based light stabilizers, benzotriazole-based ultraviolet absorbers, flame retardants, antistatic agents, organic fibers, glass fibers, carbon fibers, and metal whiskers And other reinforcing agents; colorants; other additives; or such mixtures.

The content ratio of the additive in the molded article for an optical material is preferably 0 to 5% by mass, more preferably 0 to 2% by mass, and still more preferably 0 to 1% by mass.

Further, the molded article for an optical material comprising the acrylic thermoplastic resin of the present invention may be mixed with at least one of the following resins: a polyolefin such as polyethylene or polypropylene, in a range that does not impair the object of the present invention; Styrene resin such as polystyrene, styrene-acrylonitrile copolymer; polydecylamine; polyphenylene sulfide resin; polyetheretherketone resin; polyester; polyfluorene; polyphenylene oxide; Polyethylenimine; polyether quinone; polyacetal; cellulose resin such as triacetyl cellulose; thermoplastic resin; and thermosetting properties such as phenol resin, melamine resin, silicone resin, epoxy resin, etc. Resin, etc.

The method for producing the molded article for an optical material in the present invention is not particularly limited, and a known method can be used. For example, it can be manufactured by using a single-axis extruder, a twin-screw extruder, a Banbury mixer, a Brabender, and a kneading machine such as various kneaders. Further, the unstretched molded body in the present invention can be formed by injection molding, sheet molding, blow molding, injection blow molding, inflation molding, extrusion molding. The molding is carried out by a known method such as foam molding, and a secondary processing method such as pressure forming or vacuum forming may be used.

When the shape of the molded article for an optical material of the present invention is a film or a sheet, a method such as extrusion molding or casting molding can be used. For example, the unstretched film can be extruded by using an extruder equipped with a T-die, a circular die, or the like. At the time of extrusion molding, the various additives and the resin other than the acrylic thermoplastic resin of the present invention may be melt-kneaded and molded.

Further, the acrylic thermoplastic resin of the present invention can be dissolved in a solvent such as chloroform or dichloromethane, and then the unstretched film can be cast by dry curing by casting. There is no danger of exposure to solvents such as chloroform or methylene chloride required for casting, and safety and cost, such as drying equipment and solvent recovery equipment, which are not required for drying and curing. The method for forming an optical film comprising the acrylic thermoplastic resin of the invention is preferably extrusion molding.

The obtained unstretched film may be longitudinally uniaxially extended in a mechanical flow direction, or may be horizontally uniaxially extended in a direction perpendicular to the mechanical flow direction, or may be successively biaxially extended according to the roll extension and the tenter extension. The extension method, the simultaneous biaxial stretching method of the tenter extension, the biaxial stretching method of the tubular extension, and the like are performed to extend the biaxially stretched film. The strength of the film can be increased by stretching.

The final stretching ratio can be judged based on the heat shrinkage rate of the obtained molded body. The stretching ratio is preferably 0.1% or more and less than 300% in at least one direction, more preferably 0.2% or more and 300% or less, and more preferably 0.3% or more and 300% or less. From the viewpoint of birefringence, heat resistance, and strength, a preferred elongated molded body can be obtained by designing within this range.

In the present invention, the extension can be continuously performed in extrusion molding and casting molding. Moreover, in order to stabilize the optical isotropic or mechanical properties of the molded article for optical material (for example, an optical film) of the present invention, heat treatment (annealing) or the like may be performed after stretching.

The conditions of the heat treatment are not particularly limited as long as the conditions similar to those of the conventionally known heat treatment for the stretched film are appropriately selected.

In the present invention, the difference between the film and the sheet is only the thickness, and the film means a thickness of 300 μm or less, and the sheet means a thickness of more than 300 μm. Further, the film is preferably 1 μm or more, and more preferably 5 μm or more. The sheet is preferably 10 mm or less, and more preferably 5 mm or less.

The molded article for an optical material comprising the acrylic thermoplastic resin of the present invention can be used for a liquid crystal display, a plasma display, an organic EL display, a field emission display, a rear-projection television, or the like. a polarizing plate protective film, a quarter-wave plate, a phase difference plate such as a 1⁄2 wavelength plate, a liquid crystal optical compensation film such as a viewing angle control film, a display front panel, a display substrate, a lens, or the like, or a solar cell A transparent substrate or the like used.

Others, for example, in the field of optical communication systems, optical switching systems, and optical measurement systems, can also be used for waveguides, lenses, optical fibers, coated materials for optical fibers, lenses for LEDs, lens covers, and the like. The optical material formed of the molded body of the present invention may be subjected to surface functionalization treatment such as antireflection treatment, transparent conductive treatment, electromagnetic wave shielding treatment, gas barrier treatment, and the like.

[Optical film]

An optical film obtained by molding the acrylic thermoplastic resin of the present invention has an application requiring birefringence and a need for birefringence in industrial applications. The use which does not require birefringence is, for example, a polarizing plate protective film, and the use of birefringence is, for example, a retardation film.

The optical film formed by molding the acrylic thermoplastic resin of the present invention satisfies the following optical properties (i):

(i) The absolute value of the photoelastic coefficient is 3.0 × 10 ^-12 Pa ^-1 or less. Furthermore, it is preferred to satisfy the optical properties (ii):

(ii) In the least square approximation linear relationship (a) of the extended birefringence (⊿n(S)) and the stretching ratio (S), the value of the slope K satisfies the following formula (b):

⊿n(S)=K×S+C ...(a)

∣K∣<0.30×10 ^-6 ...(b)

Furthermore, it is preferred to satisfy the optical properties (iii):

(iii) The absolute value of the phase difference (Re) in the in-plane direction is 30 nm or less. Furthermore, it is preferred to satisfy the optical properties (iv):

(iv) The absolute value of the phase difference (Rth) in the thickness direction is 30 nm or less. Furthermore, it is preferred to satisfy the optical properties (v):

(v) The ratio (Rth/Re) of the phase difference (Re) in the in-plane direction to the phase difference (Rth) in the thickness direction satisfies the following formula (c):

0.1<Rth/Re<1 ...(c)

Furthermore, it is preferred to satisfy the following condition (vi):

(vi) The glass transition temperature (Tg) is 120 ° C or higher.

Furthermore, it is preferred to satisfy the following condition (vii):

(vii) The total light transmittance is 85% or more.

The optical film of the acrylic thermoplastic resin of the present invention has an absolute value of the photoelastic coefficient of 3.0 × 10 ^-12 Pa ^-1 or less. It is preferably 2.0 × 10 ^-12 Pa ^-1 or less, more preferably 1.0 × 10 ^-12 Pa ^-1 or less.

The photoelastic coefficient has been described in various documents (for example, refer to General Chemistry, No. 39, 1998 (issued by the Japan Society for Publications)), and is defined by the following formula:

C _R =∣Δn∣/σ _R

∣Δn∣=nx-ny

(wherein, C _R : photoelastic coefficient, σ _R : tensile stress, ∣Δn ∣: absolute value of birefringence, nx: refractive index in the stretching direction, ny: refractive index perpendicular to the stretching direction).

The closer the value of the photoelastic coefficient is to 0, the smaller the change in birefringence due to the external force, which means that the change in birefringence designed in each application is small.

In the case of industrial use, in order to improve the mechanical strength of the optical film, it is preferable to perform the stretching process, and it is feared that the birefringence is increased due to the alignment caused by the stretching.

The optical film composed of the acrylic thermoplastic resin of the present invention is in the least square approximation linear relationship (a) of the birefringence (⊿n(S)) and the stretching ratio (S) after stretching, and the value of the slope K is Those who satisfy the following formula (b):

⊿n(S)=K×S+C . . . (a)

∣K∣<0.30×10 ^-6 . . . (b)

The value of this slope K represents the degree of increase in birefringence (⊿n(S)) with respect to the stretching ratio (S). When K is larger, the amount of increase in birefringence is larger with respect to stretching; the smaller the K is , the smaller the amount of increase in birefringence relative to the extension.

The preferred K value of the optical film composed of the acrylic thermoplastic resin of the present invention is ∣K ∣ < 0.30 × 10 ^-6 . Preferably, ∣K∣<0.15×10 ^-6 , more preferably ∣K∣<0.10×10 ^-6 .

Here, the value of K is a value obtained by measuring the glass transition temperature (Tg) of the thermoplastic resin measured by DSC and extending at an elongation temperature of (Tg + 20) ° C and at an elongation speed of 500 mm / minute. In general, it is known that if the stretching speed is made slow, the amount of increase in birefringence is reduced. Further, the value of K can be determined by, for example, determining the value of the birefringence (⊿n(S)) when the stretching ratio (S) is 100 times, 200 times, or 300 times, and the equivalent value is in a least square approximation. Calculate it by calculation. In addition, the extension ratio (S) is a value represented by the following formula when the distance between the chucks before the extension is L ₀ and the distance between the extensions after the extension is L ₁ :

The absolute value of the phase difference (Re) per 100 μm of the thickness of the optical film composed of the acrylic thermoplastic resin of the present invention is 30 nm or less. It is preferably 20 nm or less, more preferably 15 nm or less, and particularly preferably 11 nm or less. The absolute value of the phase difference is an indicator of the magnitude of the birefringence. Therefore, the optical film composed of the acrylic thermoplastic resin of the present invention has a small birefringence system. On the other hand, when the absolute value of the phase difference per 100 μm in the in-plane direction exceeds 30 nm, it means that the anisotropy of the refractive index is high, and it may not be used for applications requiring low birefringence.

In general, it is known that an optical film composed of a thermoplastic resin increases its phase difference due to elongation. For example, in order to increase the mechanical strength of the optical film, the stretching process may be performed. However, if the thickness of the obtained in-plane direction of the extended optical film is more than 30 nm per 100 μm, a low birefringence film cannot be obtained.

The absolute value of the phase difference (Rth) per 100 μm of the thickness of the optical film composed of the acrylic thermoplastic resin of the present invention in the thickness direction is 30 nm or less. It is preferably 20 nm or less, more preferably 15 nm or less, and particularly preferably 11 nm or less. The phase difference in the thickness direction is, for example, an index relating to the viewing angle characteristics of the display device in which the optical film is assembled. Specifically, as the absolute value of the phase difference in the thickness direction is smaller, the viewing angle characteristics are better, and the change in the hue of the display color due to the viewing angle and the decrease in contrast are less. The absolute value of the phase difference in the thickness direction of the optical film is small.

The glass transition temperature (Tg) of the optical film is preferably 120 ° C or higher. It is preferably 130 ° C or more, and more preferably 135 ° C or more. When the glass transition temperature is less than 120 ° C, there is a case where the dimensional stability at the use ambient temperature is poor, and it cannot be used for applications requiring high heat resistance.

The total light transmittance of the optical film is preferably 85% or more. It is preferably 88% or more, more preferably 90% or more. If the total light transmittance is less than 85%, there is a case where the transparency is lowered, and it cannot be used for applications requiring high transparency.

The optical properties of the optical film composed of the acrylic thermoplastic resin of the present invention are characterized by extremely small birefringence (approx. 0) in the in-plane direction of the film and in the thickness direction of the film, and the photoelastic coefficient is also extremely small (approximately 0), and The optical completeness is not achieved by a conventionally known resin. Further, high heat resistance can also be achieved.

The optical film composed of the acrylic thermoplastic resin of the present invention is mainly suitable for applications requiring no birefringence, such as a polarizing plate protective film.

(Example)

Hereinafter, the present invention will be more specifically described by way of examples.

The method for measuring each measured value used in the present invention is as follows.

(a) Analysis of thermoplastic resin (1) repeating unit

Identification by (1) a repeating unit derived from a methacrylate monomer, (ii) a repeating unit derived from a vinyl aromatic monomer, and (iii) derived from an aromatic group by ¹ H-NMR measurement The repeating unit of the acrylate monomer, and (iv) the cyclic acid repeating unit, and calculating the amount thereof.

Measuring machine: DPX-400 manufactured by Bruker Co., Ltd.

Determination of solvent: CDCl ₃ , or d ⁶ -DMSO

Measuring temperature: 40 ° C

(2) Glass transition temperature

The glass transition temperature (Tg) was obtained by using a differential scanning calorimeter (Diamond DSC manufactured by PerkinElmer Co., Ltd.) under a nitrogen atmosphere with α-alumina as a reference, and according to JIS-K-7121, a sample of about 10 mg was used. The temperature increase rate of 10 ° C / min was raised from normal temperature to 200 ° C, and the obtained DSC curve was calculated by the midpoint method.

(3) Molecular weight

The weight average molecular weight and the number average molecular weight were determined by using a gel permeation chromatography apparatus (HLC-8220, manufactured by Tosoh Corp.), a solvent of tetrahydrofuran, and a set temperature of 40 ° C, which was obtained by conversion from a commercially available standard PMMA.

(b) Optical property evaluation (1) Production of optical film samples

a) Forming of press film

Using a vacuum compression molding machine (SFV-30 type manufactured by Shinto Metal Industry Co., Ltd.), preheating at 260 ° C for 25 minutes under atmospheric pressure, and then performing vacuum treatment (about 10 kPa) at 260 ° C for 10 minutes at 10 MPa. Compressing, and forming the film.

b) forming of the stretch film

The stretched film was formed by a single-axis free extension at an extension temperature (Tg + 20) ° C and an elongation speed (500 mm / minute) using a 5t tensile tester manufactured by Instron Co., Ltd. The extension was performed at extension ratios of 100%, 200%, and 300%.

(2) Determination of birefringence

The RETS-100 manufactured by Otsuka Electronics Co., Ltd. was used and measured by a rotating analyzer method. The value of birefringence is the value of light having a wavelength of 550 nm. The birefringence (Δn) is calculated according to the following formula:

Δn=nx-ny

(Δn: birefringence, nx: refractive index in the stretching direction, ny: refractive index perpendicular to the stretching direction);

The absolute value of birefringence (Δn) (∣Δn∣) is obtained by the following equation:

∣Δn∣=∣nx-ny∣

(3) Determination of phase difference <In-plane phase difference>

The RETS-100 manufactured by Otsuka Electronics Co., Ltd. was used, and the measurement was carried out by a rotary analyzer method at a wavelength of 400 to 800 nm.

The absolute value of birefringence (∣Δn∣) has the following relationship with the phase difference (Re):

Re=∣Δn∣×d

(∣Δn∣: absolute value of birefringence, Re: phase difference, d: thickness of the sample).

In addition, the absolute value of birefringence (∣Δn∣) is the value shown below:

∣Δn∣=∣nx-ny∣

(nx: refractive index in the direction of extension, ny: refractive index in the plane and perpendicular to the direction of extension).

<Phase difference in thickness direction>

The phase difference measuring device (KOBRA-21ADH) manufactured by Oji Scientific Instruments Co., Ltd. was used to measure the phase difference at a wavelength of 589 nm, and the obtained value was converted into a film thickness of 100 μm to obtain a measured value.

The absolute value of birefringence (∣Δn∣) has the following relationship with the phase difference (Rth):

Rth=∣Δn∣×d

(∣Δn∣: absolute value of birefringence, Rth: phase difference, d: thickness of the sample).

In addition, the absolute value of birefringence (∣Δn∣) is the value shown below:

∣Δn∣=∣(nx-ny)/2-nz∣

(nx: refractive index in the extending direction, ny: refractive index in the plane and perpendicular to the extending direction, nz: refractive index in the thickness direction perpendicular to the extending direction).

(In an ideal state, in the film in which the three-dimensional direction is completely isotropic, the in-plane phase difference (Re) and the thickness direction phase difference (Rth) are both 0).

(4) Determination of photoelastic coefficient

The birefringence measuring apparatus described in detail in Polymer Engineering and Science 1999, 39, 2349-2357 is used. The film stretching device was placed in the path of the laser light, and the birefringence was measured while applying a tensile stress at 23 °C. The strain rate at the time of stretching was 50%/min (between the chucks: 50 mm, the moving speed of the chuck: 5 mm/min), and the width of the test piece was 6 mm. From the relationship between the absolute value of birefringence (∣Δn∣) and the tensile stress (σ _R ), the slope of the straight line is obtained by the least square approximation method, and the photoelastic coefficient (C _R ) is calculated. In the calculation, the data between the tensile stresses of 2.5 MPa ≦ σ _R ≦ 10 Mpa was used.

C _R =∣Δn∣/σ _R

∣Δn∣=∣nx-ny∣

(C _R : photoelastic coefficient, σ _R : tensile stress, ∣Δn∣: absolute value of birefringence, nx: refractive index in the stretching direction, ny: refractive index perpendicular to the stretching direction)

[thermoplastic resin] Methyl methacrylate/styrene/benzyl methacrylate/maleic anhydride [Example 1]

A glass reactor (capacity 1 L) with a stirrer, a temperature sensor, a cooling tube, a nitrogen introduction nozzle, a raw material solution introduction nozzle, a starter solution introduction nozzle, and a polymerization solution discharge nozzle was used. The pressure of the polymerization reactor was slightly pressurized, and the reaction temperature was controlled at 100 °C.

518 g of methyl methacrylate (MMA), 48 g of styrene (St), 9.6 g of benzyl methacrylate (BzMA), 384 g of maleic acid (MAH), 240 g of methyl isobutyl ketone, n-octyl After mixing 1.2 g of mercaptan, the raw material solution was prepared by substituting with nitrogen. 0.364 g of 2,2'-azobis(isobutyronitrile) was dissolved in 12.96 g of methyl isobutyl ketone, and then substituted with nitrogen to prepare a starter solution.

The raw material solution was introduced from the raw material solution introduction nozzle at 6.98 ml/min using a pump. Further, the initiator solution was introduced using a pump and introduced into the nozzle from the initiator solution at 0.08 ml/min. After 30 minutes, the polymer solution was discharged from the polymerization solution discharge nozzle using a pump at a flow rate of 425 ml/hour.

The discharge amount of 1.5 hours after the start of the discharge of the polymer solution was separately recovered in the primary flow tank. The polymer solution will be officially recovered from the beginning of the discharge for 1.5 hours to 2.5 hours. The obtained polymer solution was dropped into methanol which is a poor solvent, and precipitated and purified. The objective thermoplastic resin was obtained by drying at 130 ° C for 2 hours under vacuum.

Composition: MMA/St/BzMA/MAH=61/12/1/27 wt%

Molecular weight: Mw = 18.8 × 10 ⁴ ; Mw / Mn = 2.08

Tg: 142 ° C

The ¹ H-NMR spectrum of this material is shown in Fig. 1.

[Embodiment 2]

In the same manner as in Example 1, except that 509 g of methyl methacrylate, 48 g of styrene, 19 g of benzyl methacrylate, and 384 g of maleic anhydride were changed, a thermoplastic resin was obtained.

Composition: MMA/St/BzMA/MAH=62/12/2/24% by weight

Molecular weight: Mw = 17.3 × 10 ⁴ ; Mw / Mn = 2.13

Tg: 141 ° C

[Example 3]

In the same manner as in Example 1, except that 499 g of methyl methacrylate, 42 g of styrene, 48 g of benzyl methacrylate, and 371 g of maleic anhydride were changed, a thermoplastic resin was obtained.

Composition: MMA/St/BzMA/MAH=60/11/5/24% by weight

Molecular weight: Mw = 20.2 × 10 ⁴ ; Mw / Mn = 2.36

Tg: 138 ° C

[Comparative Example 1]

In the same manner as in Example 1, except that 469 g of methyl methacrylate, 37 g of styrene, 96 g of benzyl methacrylate, and 358 g of maleic anhydride were changed, a thermoplastic resin was obtained.

Composition: MMA/St/BzMA/MAH=59/7/12/22% by weight

Molecular weight: Mw = 18.0 × 10 ⁴ ; Mw / Mn = 2.12

Tg: 133 ° C

[Comparative Example 2]

In the same manner as in Example 1, except that benzyl methacrylate was not used and 768 g of methyl methacrylate, 144 g of styrene, and 48 g of maleic anhydride were used, a thermoplastic resin was obtained.

Composition: MMA/St/MAH=76/17/7 wt%

Molecular weight: MW = 13.4 × 10 ⁴ ; MW / Mn = 2.01

Tg: 128 ° C

Methyl methacrylate/styrene/benzyl methacrylate/methacrylic acid/glutaric anhydride [Example 4]

A glass reactor (capacity 1 L) with a stirrer, a temperature sensor, a cooling tube, a nitrogen introduction nozzle, a raw material solution introduction nozzle, a starter solution introduction nozzle, and a polymerization solution discharge nozzle was used. The pressure of the polymerization reactor was slightly pressurized, and the reaction temperature was controlled at 100 °C.

900 g of methyl methacrylate, 36 g of styrene, 48 g of benzyl methacrylate, 216 g of methacrylic acid (MAA), 240 g of methyl isobutyl ketone, and 1.2 g of n-octyl mercaptan were mixed and replaced with nitrogen. The raw material solution was prepared. 0.364 g of 2,2'-azobis(isobutyronitrile) was dissolved in 12.96 g of methyl isobutyl ketone, and then substituted with nitrogen to prepare a starter solution.

The raw material solution was introduced from the raw material solution introduction nozzle at 6.98 ml/min using a pump. Further, the initiator solution was introduced using a pump and introduced into the nozzle from the initiator solution at 0.08 ml/min. After 30 minutes, the polymer solution was discharged from the polymerization solution discharge nozzle using a pump at a flow rate of 425 ml/hour.

The discharge amount of 1.5 hours after the start of the discharge of the polymer solution was separately recovered in the primary flow tank. The polymer solution will be officially recovered from the beginning of the discharge for 1.5 hours to 2.5 hours. The obtained polymer solution was dropped into methanol which is a poor solvent, and precipitated and purified. The precursor was obtained by drying at 130 ° C for 2 hours under vacuum. The precursor was subjected to heat treatment (treatment temperature: 250 ° C, vacuum degree: 133 hPa (100 mmHg)) with a Labo PlaStomill equipped with a devolatilizer to obtain a desired thermoplastic resin.

Composition: MMA/St/BzMA/MAA/glutaric anhydride=70/5/4/21% by weight

Molecular weight: Mw = 11.4 × 10 ⁴ ; Mw / Mn = 2.40

Tg: 128 ° C

[Comparative Example 3]

In Example 4, a thermoplastic resin was obtained in the same manner as in Example 4 except that benzyl methacrylate was not used and changed to 888 g of methyl methacrylate, 60 g of styrene, and 252 g of methacrylic acid.

Composition: MMA/St/MAA/glutaric anhydride = 64/9/4/23% by weight

Molecular weight: Mw = 10.0 × 10 ⁴ ; Mw / Mn = 2.09

Tg: 131 ° C

[Comparative Example 4]

In the same manner as in Example 1, except that 960 g of methyl methacrylate was used, a thermoplastic resin was obtained.

Composition: MMA=100% by weight

Molecular weight: Mw = 10 × 10 ⁴ ; Mw / Mn = 1.89

Tg: 121 ° C

The polymerization results of these are shown in Table 1.

[Examples 5 to 8, Comparative Examples 5 to 8]

The thermoplastic resins obtained in Examples 1 to 4 and Comparative Examples 1 to 4 were molded into a film according to the aforementioned method. The film was formed into a 100% stretched film according to the aforementioned method, and its optical characteristics were evaluated. The measurement results are shown in Table 2.

The optical film composed of the acrylic thermoplastic resin of the present invention has a low birefringence and a photoelastic coefficient both in terms of optical properties, and is composed of an acrylic thermoplastic resin of a comparative example. The optical film has, for example, a large photoelastic coefficient and poor optical characteristics (x).

Further, according to the results of Examples 5 to 8 and Comparative Example 1, it was confirmed that the photoelastic coefficient was controlled by the benzyl methacrylate content, and when the benzyl methacrylate content was in the range of 0.1 to 5% by weight. The absolute value of the photoelastic coefficient is a minimum value of 2.0 × 10 ^-12 Pa ^-1 or less. In the prior art, a method of adjusting the photoelastic coefficient by adding an organic low molecular compound has been disclosed, for example, in Japanese Laid-Open Patent Publication No. 2007-169622, but in the method, when performing forming processing or as an optical material When it is used as a molded body, it is still possible to cause a change in optical characteristics due to bleeding of the added compound or the like. In the acrylic thermoplastic resin of the present invention, since the component which regulates the photoelastic coefficient is copolymerized in the polymer main chain, bleeding or the like is unlikely to occur, and the optical characteristics of stability can be exhibited.

[Examples 9 and 10, Comparative Example 9]

The thermoplastic resins obtained in Example 1, Example 3, and Comparative Example 4 were molded into a film according to the above method. The film was formed into a 100%, 200%, and 300% stretched film by the above method, and its optical characteristics were evaluated. The measurement results are shown in Table 3.

[Example 11]

A thermoplastic resin obtained by the same operation as in Example 1 was used, and an extruder equipped with a T-die manufactured by Technovel Co., Ltd. (KZW15TW-25MG-NH type/with a T-die/thickness thickness of 150 mm in width) The resin temperature in the cylinder of the extruder of 0.5 mm) was adjusted with the temperature of the T-die to perform extrusion molding. The obtained extruded film was formed into a 100%, 200%, and 300% stretched film according to the above method (and the elongation speed was appropriately changed), and the optical characteristics were evaluated. The measurement results are shown in Table 4.

The optical film composed of the acrylic thermoplastic resin of the present invention has excellent heat resistance, and its optical characteristics (very small birefringence value and extremely small photoelastic coefficient) also have high optical isoelectricity which has not been conventionally obtained. Further, it was also confirmed that the rate of change in birefringence when the film was arbitrarily stretched at the time of molding or after molding was extremely small. This feature is not affected by the alignment caused by the flow during melt forming, even when the film is formed by extrusion molding or the subsequent stretching process, and is extremely advantageous in the feature of "no birefringence". .

These characteristics are suitable for use as a polarizing plate protective film or the like.

[Examples 12 and 13]

The stretched film obtained in Example 5 was allowed to stand in an atmosphere at a temperature of 80 ° C and a humidity of 90% to prepare two kinds of stretched films having different hydrolysis rates, and the optical properties were evaluated. The measurement results are shown in Table 5.

It is understood that the hydrolysis rate of the optical film composed of the acrylic thermoplastic resin of the present invention can sufficiently maintain its low birefringence as long as it is less than 10 mol%.

(industrial availability)

The molded article for an optical material comprising the acrylic thermoplastic resin of the present invention has high heat resistance and excellent optical properties, and exhibits industrially advantageous melt formability, and thus can be suitably used for a liquid crystal display, a plasma display, and an organic EL. a polarizing plate protective film, a quarter-wave plate, a phase difference plate such as a 1⁄2 wavelength plate, a liquid crystal optical compensation film such as a viewing angle control film, a display front panel, and the like used in displays such as a display, a field emission display, and a rear projection type television. A display substrate, a lens, or the like, or a transparent substrate used in a solar cell.

Others, for example, in the field of optical communication systems, optical switching systems, and optical measurement systems, can also be used for waveguides, lenses, optical fibers, coated materials for optical fibers, lenses for LEDs, lens covers, and the like.

Fig. 1 is a ¹ H-NMR spectrum chart of an acrylic thermoplastic resin (Example 1).

No component symbol

Claims (17)

An acrylic thermoplastic resin containing 10 to 70% by weight of a repeating unit derived from a methacrylate monomer represented by the following formula (1), and a vinyl aromatic group derived from the following formula (2) 5 to 40% by weight of the repeating unit of the monomer, 0.1 to 5% by weight of the repeating unit derived from the methacrylic ester monomer having an aromatic group represented by the following formula (3), and the following formula (4) or The cyclic acid anhydride repeating unit represented by the following formula (5) is 20 to 50% by weight, and the weight average molecular weight measured by the GPC measurement is in the range of 70,000 to 400,000, and the molecular weight distribution is in the range of 1.8 to 3.0. Therefore, the weight average molecular weight measured by the GPC measurement method is obtained by using tetrahydrofuran as a solvent, setting the temperature to 40 ° C, and converting the polymethyl methacrylate as a standard sample; (wherein R ¹ represents hydrogen, a linear or branched chain having 1 to 12 carbon atoms, and a carbon number of 5 to 12 cycloalkyl groups) (wherein R ² and R ³ each may be the same or different and represent a hydrogen, a halogen, a hydroxyl group, an alkoxy group, a nitro group, a linear or branched chain having an alkyl group having 1 to 12 carbon atoms; and 1 represents 1; To the integer of 3) (wherein R ⁴ represents hydrogen, halogen, hydroxy, alkoxy, nitro, a linear or branched chain having 1 to 12 carbon atoms; m represents an integer of 1 to 3, and n represents 0 to 2 Integer) (wherein R ⁵ to R ⁸ may be the same or different, respectively, and represent an alkyl group having 1 to 12 carbon atoms in a hydrogen, a linear or a branched chain). The acrylic thermoplastic resin according to claim 1, wherein the content of the repeating unit derived from the vinyl aromatic monomer (A) and the content of the cyclic anhydride repeating unit (B) are molar ratio (B/ A) is greater than 1 and below 10. The acrylic thermoplastic resin according to claim 1 or 2, wherein the repeating unit derived from the methacrylate monomer is derived from methyl methacrylate derived from a vinyl aromatic monomer. The repeating unit is derived from styrene, and the repeating unit derived from the methacrylate monomer having an aromatic group is derived from benzyl methacrylate, and the cyclic anhydride repeating unit is derived from maleic anhydride. The acrylic thermoplastic resin according to claim 1 or 2, which satisfies the optical properties of the following (i): (i) the absolute value of the photoelastic coefficient is 3.0 × 10 ^-12 Pa ^-1 or less. An acrylic thermoplastic resin according to claim 1 or 2, which is an optical property satisfying the following (ii): (ii) birefringence after stretching (⊿n(S)) and stretching ratio In the least square approximation linear relation (S) of (S), the value of the slope K satisfies the following formula (b): ⊿n(S)=K×S+C...(a) | K |<0.30 ×10 ^-6 .........(b). The acrylic thermoplastic resin according to claim 1 or 2, which further satisfies the optical properties of the following (iii): (iii) the absolute value of the phase difference (Re) in the in-plane direction is 30 nm or less. The acrylic thermoplastic resin according to claim 1 or 2, which further satisfies the optical properties of the following (iv): (iv) the absolute value of the phase difference (Rth) in the thickness direction is 30 nm or less. The acrylic thermoplastic resin according to claim 1 or 2, which further satisfies the optical properties of (v) below: (v) the phase difference (Re) in the in-plane direction and the phase difference in the thickness direction ( The ratio (Rth/Re) of Rth) satisfies the following formula (c): 0.1 < Rth / Re < 1 (...). For example, the acrylic thermoplastic resin of claim 1 or 2, which meets the following conditions (vi): (vi) The glass transition temperature (Tg) is 120 ° C or higher. The acrylic thermoplastic resin according to item 1 or item 2 of the patent application, which further satisfies the following condition (vii): (vii) the total light transmittance is 85% or more. A molded article for an optical material, which comprises the acrylic thermoplastic resin according to any one of claims 1 to 10. The molded article for an optical material according to claim 11, which is an optical film. The molded article for an optical material according to claim 12, wherein the optical film is a film formed by extrusion molding, and is formed to extend at least in a uniaxial direction, and has a stretching ratio of 0.1 to 300%. The molded article for an optical material according to claim 12, wherein the optical film is a film formed by casting, and is formed to extend at least in a uniaxial direction, and has a stretching ratio of 0.1 to 300%. The molded article for an optical material according to claim 12, wherein the optical film is a polarizing plate protective film. The molded article for an optical material according to claim 12, wherein the optical film is a retardation film. A molded article for an optical material according to claim 11 which is an optical lens.